Aceman, or The Viscoelastic Warrior: Aceman, is a fictional anime-hero in the universe of Deadman Wonderland. Ganta and Shiro were big fans of him when they were children, and they used to reenact his fighting scenes. Senji has also admitted he looked up to Aceman.
Sometimes when Shiro saves Ganta, she impersonates Aceman by saying: "Aceman is here!". His trademark feature is his long attack names (ex. "Super ultra delicious dynamite kraken gaki special atomic bomber spiral core poisoned drill gravity air spin fire flare vibrating spectacular final yogurt electronic synchro dive jumping beam happy zero heat ice crusher terry itou stone mountain surging dark candle freeze buster light sun ocean remarkable clear clip cutter jab Gazelle Monkey Boar Coleacnth Stardust Poison Papiko Sunder Storm Enlightend over-named but really nothing but an extremely normal PUNCH!"), which Ganta and Shiro were very fond of.
10 years in the past, when Ganta and Shiro were still living in the hospital, Ganta wanted to play with Shiro and Aceman, but Shiro was in pain and slapped the doll out of Ganta's hand, breaking it. Ganta became sad and angry, and went outside to eat his pudding alone. However, he was attacked by a mad dog (who was clearly a test subject and exhibited symptoms similer to Hagire's second generation body near the end of its life) and was in danger. Ganta called out for Aceman in fear and Shiro jumped out of a window onto the dog, knocking the beast out cold. Shiro then made a pose and said: "Have no fear. Aceman is here." After that, they repaired the Aceman-doll and ate pudding together.
Because Shiro sees herself as Aceman when rescuing someone, the Wretched Egg, her second personality, dressed herself similar to Aceman.